Production of luminescent screens

ABSTRACT

Process for the production of luminescent screens for color television tubes, the improvement comprising the use of lightinsensitive ethylenically unsaturated vinyl compounds as the binder material, said compounds being capable of undergoing a hardening action when subjected to corpuscular radiation.

United States Patent 1 1 1111 3,776,754 Levinos Dec. 4, 1973 [541PRODUCTION OF LUMINESCENT 3,003,873 10 1961 Zworykin 117 33.s CM NS3,527,652 9/1970 Ozaki et al.. 96/36.1 2,727,828 12/1955 Law 117/33.5 CMInventor: Steven Levmos, C NJ. 3,630,868 12/1971 Marans 117/93.31

3,62 12 1971 [73] Ass'gnem GAF comramn New York 3,273, 63?) 9/1966 1 177 9 313 [22] Filed; July 22, 1971 3,247,012 4/1966 Burlant 117/93.31

[21] Appl. No.: 165,319

Primary Examiner--Wi1liam D. Martin kehftcd Application Data AssistantExaminerJohn H. Newsome [63] Continuatlon of Ser. No. 679,617, Nov. 1,1967, Attorney walter C Kehm and Samson B Leavm at abandoned.

a1. [52] 11.8. C1. 117/33.5 CM, 96/1 E, 96/36.l, 117/93.3l, 117/161 UA,117/161 UB, 117/161UC,1l7/161UE,117/161UF,

117/161 UN, 117/161 UZ [57] ABSTRACT [51] 'f Bm 1/ Cosf 3/00 H011 29/22Process for the production of luminescent screens for [58] Fleld ofSearch 117/93.31, 33.5 CM, color television tubes the improvementcomprising 117/161 16] 161 161 UB5 the use of light-insensitiveethylenically unsaturated l E vinyl compounds as the binder material,said compounds being capable of undergoing a hardening ac- [56]References cued tion when subjected to corpuscular radiation.

UNITED STATES PATENTS 2,897,089 7/1959 Ahlburg et a1 117/33.5 CM 5Claims, N0 Drawings PRODUCTION OF LUMINESCENT SCREENS This applicationis a streamlined continuation of prior co-pending application Ser. No.679,617, filed Nov. 1, 1967, and now abandoned.

The present invention relates in general to the manufacture of colortelevision picture tubes and in particular to the provision of improvedcompositions and processing for such purposes. I

As is well known, phosphor glass screens of the type commonly employedin the fabrication of color television picture tubes comprise a plateprovided with finely discrete patterns of three different phosphors eachof which is capable of emitting radiation of a different primary color,i.e., red, green and blue. In general, tubes of this nature areconstructed in such fashion that a thin perforated metal mask is mountedparallel to the screen and a short distance away from the screen towardthe gun end of the tube, such metal mask being provided with aconcatenation of holes. Each of the holes provided in the metal maskcorresponds to each of the primary colors, i.e., is positioned toilluminate a trio of red, green and blue emitting phosphor dotscomprising a single unit of the aggregate phosphor do't pattern carriedby the luminescent screen. In addition, three electron guns are mountedsymmetrically about the axis of the tube. Each of the gun, mask anddotted screen elements are positioned in such manner that the electronbeam from each gun is directed through the holes in the mask so as tostrike phosphor dots of one primary color only.

Methods for the production of color television picture tubes of theaperture mask type are legion being extensively described in the priorart both patent and otherwise. For purposes of general classification,such methods are acknowledged to fall within one of three categories,namely, those based upon photographic reproduction techniques and silkscreen printing respectively as well as numerous other processescurrently considered to be of lesser commercial importance, e.g.,letterpressprinting, electrostatic printing, methods involving thesettling of phosphors through masks, etc.

Although the methodology thus-far promulgated in regard to colortelevision tube manufacture is found in the vast majority of instancestoprovide satisfactory re sults, certain limitations which inhei'e inthe very nature of such processing have nevertheless been confrontedwhich tend to circumscribe severely the tube manufactures scope ofoperation with respect to for example, selection of the materialsessential to the implementation of such methods, the processingconditions necessary for optimum performance, etc. For example, it hasbeen ascertained that thesilk screen process is limited, for efficaciouspractice, to those applications wherein the plate employed as thesupport for the phosphor screen pattern is absolutely flat or planar.Consequently, processes of this type are sustantially inapplicable assuch in those instances involving the use of a plate element of arcuateor otherwise irregular configuration. The gravity of this particularlimitation becomes acutely evident when it is realized that much of theindustrial endeavor relating to the manufacture of color televisiontubes is specifically concerned with the fabrication of non-planarpicture tube surfaces and particularly when the latter is of relativelylarge size. Color television picture tube technology has established toa reasonable certainity that picture tubes of arcuate as distinguishedfrom planar configuration provide a much more highly efficient andpractical tube structure. However, prior industrial efforts to extendthe applicability of the silk-screen picture tube manufacturing processfor the production of curved television tube surfaces have for the mostpart met with but marginal success. Invariably, 'resort to complex ifnot highly expensive ramifications, modifications, etc. of the basictechnique is made necessary in order to implement such processing withany degree of efficacy.

In contradistinction, color television picture tube manufacturing basedupon photographic reproduction methods has met with a fairly impressivemeasure of commercial success. In general, such methods are implementedby the utilization of a photosensitive organic carrier or binder which,in the presence of a suitable catalyst material, undergoes a change insolubility characteristics as a direct result of actinic exposure. Suchcarriers or binders are often referred to in the art as colloidcarriers, the quoted term connoting resinous materials of syntheticderivation or natural origin, with typical representatives includingpolyvinyl alcohol, gelatin and the like. The requisite level oflight-sensitivity is ordinarily imparted to the binder component by theincorporation of a suitable sensitizing agent such as potassium orammonium dichromate. The binder material thus sensitized is thereafterapplied to the inside surface of the television picture tube viewingpanel by any one of several conventional coating techniques, e.g.,flowing, spraying, whirling, etc. Any excess coating material canthereafter be readily removed by draining or spinning in a whirl coateruntil a uniform and even surface is obtained. It will be understood thatthe selection of a particular coating technique maywell obviate anynecessity for the use of auxiliary expedients whereby to obtain an evencoating; thus, in the case of spray coating, the removal of excesslight-sensitive binder may be easily accomplished by merely controllingthe quantity of coating deposited by the spray applicator whereasuniformity of coating application may be controlled by judiciousselection of the spray pattern. Upon completion 'of the coatingoperation and prior to drying of the coating thus deposited, i.e., whilesuch coating remains in a moist or tacky state, a uniform screen of drypowered luminescent phosphor, e.g., green phosphor of the i typecommonly use d,'is sprayed "or otherwise deposited upon the tacky,radiation energy-sensitive layer. The phosphor-containing coating isthen dried by conventional means and thereupon exposed to a radiant en-.ergy source through a conventional shadow mask. The

latent-image dot pattern thus laid down represents the illuminationlocus or excitation area for one of the three primary colors, i.e., red,green or blue corresponding to one of the three cathode emitters of thetricolor tube. The final step involved in the formation of the phosphorpattern comprises the development operation wherein the entire surfaceof the panel is subjected to a wash-out operation, i.e., washed with adeveloping fluid such as deionized water, this treatment serving toremove the unhardened or non-exposed areas'of the coating whilepermitting the exposed or hardened areas to remain intact. Theaforedescribed chronology of operations is then repeated in its entiretyfor each of the remaining primary color aspects. In this manner there isobtained a complete tricolor pattern. As will be recognized, the dotpatterns corresponding to the remaining primary color aspects, in thiscase the blue and red additive primary color aspects, conform inarrangement, i.e., distribution, pattern, etc., to the blue and redcathode emitters respectively of the tricolor tube. I

It will be appreciated of course that a number of ramifications to theaforedescribed basic procedure are exploited on a commercial scale. Forexample, one such ramification involves as an essential expedient theactinic exposure of the radiation-sensitive coating prior to drying,i.e., while such coating remains in a tacky condition. Upon completionof the exposure, a uniform screen of dry powdered phosphor is sprayed orotherwise deposited upon the coating surface. Again, the terminal pointin the processing would comprise the development operation wherein theexposed and sprayed surface is treated with deionized water or othersuitable solution whereby to effect physical removal of the unexposed,unhardened coating areas. The entire sequence of operations would thenbe repeated for each of the remaining primary color aspects in themanner hereinbefore described.

A still further ramification to the aforedescribed basic procedure andone currently enjoying relatively wide-spread commercial exploitation,involves as a signal feature, the utilization of the phosphor materialin the form of a mixture, e.g., slurry or dispersion in the bindermaterial. According to such method, the phosphor is provided in the formof a preliminary slurry or dispersion with the binder material, admixingbeing effected according to conventional techniques, the filmformingcomposition being thereafter applied to the inside surface of thepicture tube panel by flowing or whirling. Following removal of excesscoating by drain-' ing or spinning the coated layer thus obtained isexposed and developed in the manner previously delineated, the involvedsequence of operation being repeated for each of the primary coloraspects.

The processing subsequent to the laying down of the tricolor phosphorpattern and incidental to the obtention of a final color televisionpicture tube unit is for the most part involving, for example, the usualsteps of lacquering, aluminizing, inserting the shadow mask, sealingboth sections of the tube to form an integral unit and finally,evacuating and baking at a temperature sufficient to burn away thebinder.

Despite the fact that color television picture tube manufacturingoperations of the aforedescribed type have met with a significantmeasure ofcommercial success, certain disadvantages and shortcomingshave nevertheless been encountered in practice which tend to detractsignificantly from their commercial feasibility V and desirability.Perhaps the most serious objection relates to the nature of thesensitizing material employed for purposes of imparting the requisitespectral response to the composition. To a great extent, commercialoperations, as presently embodied, rely almost invariably upon the useof alkali metal dichromate sensitizing agents in combination withpolyvinyl alcohol resin binders for use in the manufacture ofluminescentscreens for color television tubes. However, prior attempts to produceluminescent screens possessed of optimum luminosity, brilliance, etc.have, practically without exception been vitiated due to the fact thatresidual chromium, in significant quantities, remains in thelight-hardened areas of the coating. Unless removed at some phase ofscreen manufacture, e.g., development, wash-out, etc., such fugitivechromium remains present in the form of an oxide the latter resulting ina serious loss of brilliance of the phosphor material on electronicexcitation. Such a situation is of course of critical import since itdirectly affects the viewing quality of the picture tube. Thedeleterious effects thus resulting are further aggravated by the factthat the point-to-point density distribution of the fugitive chromiummay vary significantly with the concomitant result that not only ispicture contrast seriously impaired, but more importantly, the capacityof the luminescent screen to accurately reflect the color componentvalues directly attributable to electronic excitation is seriouslyreduced. Without intending to be bound by any theory, the followinghypotheses have nevertheless been postulated in explanation of theforegoing situation. Eder, in an article published many years agorelating to quantitative studies of brichromated gelatin, concluded thatbichromates in the presence of oxidizable organic matter tend to undergodecomposition according to a series of relatively complicated reactionsresulting in the formation of neutral chromates as well as a chromicchromate, m CrO .n Cr O wherein m and n represent numericalcoefficients, the latter compound further decomposing into chromic acidand green chromium oxide as a result of subsequent washing. The neutralchromate and chromic acid are, according to theoretical exposition,carried away by the water employed during the wash-out step. Thechromium oxide, however, combines with the carrier or binder resultingin the formation of an insoluble complex, the reactions hypothesizedtherefor being the following:

light CrzO7- CrOr m CrOg-n Cr O;

colloid removed by washing e CrO; CnOa hardened colloid colloidAccording to further evidence gathered by Popovitski, the product wasidentified as 4 Cr O 3 CrO which was presumed'to result according to thefollowing reactions:

Regardless of the reaction mechanism actually responsible for thepresence of fugitive chromium, there is ample evidence to indicate thatapproximately 19 percent of the total dichromate salt sensitizeremployed in the initial charge remains in the cross-linked polyvinylalcohol in the form of the insoluble chromic oxide. In addition, it hasbeen estimated that almost 22 percent of the dichromate salt sensitizerremains behind as the insoluble chromic oxide in those instances whereinammonium dichromate is employed as the photosensitizer. The use oflight-sensitive catalysts presents the further disadvantage that aconsiderable cost increment results since such materials are invariablyquite expenswe.

Thus, in an effort to circumvent theor foregoing problems, the use ofbinder compositions sensitive to radiation of corpuscular nature, e.g.,electron beam, has been suggested for use in color television tubemanufacture. The corpuscular radiation serves to provide the requisitequantity of energy necessary to effect insolubilization of the bindercomponent, e.g., by crosslinking of organic polymeric constituents,polymerization of monomeric constituents, etc. Methods of this typealthough ameliorating somewhat the problems attendant upon the use ofphotosensitive binder composi tions nevertheless pose rather seriousproblems to the processor, such problems finding their genesis in theinherent light-sensitivity of the resin component.

The practical significance of the foregoing will be made readilymanifest in the following description. In those methods of colortelevision tube manufacture wherein the red, green and blue phosphorsare initially provided in the binder composition to be subjected toelectron beam exposure, it is of course imperative that the radiantemissions of each of the phosphors be inconsequential, i.e., that thecomposition be insensitive to the light emitted by such phosphors. Thisis essential in order to assure that the totality of hardening action isattributable solely to the direct effects of the exposure beam. Anydeparture from such condition would involve as an unavoidable.consequence the insolubilization of binder in non-image areas and/orexcessive hardening due to overexposure. Thus, it has been determinedthat the polymeric binder materials thus far provided in the art exhibitan appreciable sensitivity to the radiant emissions of the phosphorparticles, the blue phosphor being particularly offensive in this regardsince its locus of emissions emanates from the violet-blue portion ofthe spectrum. The foregoing thus precludes the use of the blue-emittingphosphor in the binder composition prior to electronbeam exposure sincethe light emitted by the blue phosphor upon electron beam excitationwould cause non-purposive and inadvertent exposure effects, the latter,in all probability, resulting in undesired growth in dot dimension.Continued exposure would of course aggravate this tendency. Thus, as apractical necessity, the use of binder compositions possessed ofappreciable lightsensitivity imposes the burdensome restriction thatelectron beam exposure be carried out in the absence of phosphor, thelatter being applied in a separate operation subsequent to'expo'sure.Processing is of course encumbered while the economic consequencesinvolved may well be prohibitive.

A further disadvantage characterizing the methods heretofore providedinthe art inheres in the nature of the resist-forming material. Thus, theethylenically unsaturated compounds heretofore proposed for such use areadapted for solvent removal techniques wherein the solvent comprises anorganic material. This, of course,

poses a significant disadvantage since such'solvent materials areinvariably costly, difficult to handle, store,

etc. and very often present considerable health hazards to personnel.Consequently, processing is correspondingly burdened in view of thespecial precautions which must necessarily be excercised with regard tothe use of organic solvent media.

In an effort to overcome or otherwise alleviate the foregoing andrelated disadvantages, considerable industrial activity has centeredaround the research and development of more effective methods,materials, etc. for the production of luminescent screens for colortelevision picture tubes. Although much in the way of meritoriousachievement has characterized the efforts thus far expended in thisregard, the problems surrounding the obtention of luminescent screenshaving I 6 the desired degree of brilliance, luminosity, etc. continueto challenge tube-manufacturing technology.

In accordance with the discovery forming the basis of the presentinvention, it has been ascertained that the use of a relativelydelimited class of ethylenically unsaturated organic material havingpredetermined spectral sensitivity characteristics and capable ofundergoing insolubilization when subjected to corpuscular radiationmakes possible optimum realization of the manifold advantages inherentin resist forming techniques based upon the use of corpuscular radiationwhen applied to color television tube manufacture, while eliminating theproblems associated with spurious hardening effects typifying theprocedures heretofore provided in the art.

Thus, a primary object of the present invention resides in the provisionof compositions and processing uniquely and beneficially adapted for usein connection with the manufacture of luminescent tricolor screens forcolor television picture tubes wherein the foregoing and relateddisadvantages are eliminated or at least mitigated to a substantialextent.

Another object of the present invention resides in the provision of aprocess for the preparation of color television tubes wherein problemsassociated with residual metal contamination are eliminated.

Yet another object of the present invention resides in the provision ofa process for the preparation of color television tubes capable orproviding sharp dot patterns of excellent brightness.

A further object of the present invention resides in the provision of aprocess for the preparation of luminescent screens for color televisiontubes comprising polymeric resists and wherein any necessity for theutilization of organic solvent media in developing the resist image iscompletely obviated.

A still further object of the present invention resides in the provisionof a process for color television tube manufacture capable ofexpeditious implementation and wherein any necessity for post-exposureincorporation of phosphor into the binder'composition is completelyobviated.

Further objects and advantages of the present invention will becomeapparent hereinafter as the description proceeds. I

' The attainment of the foregoing and related objects is made possiblein accordance with the present invention which in its broaded aspectsincludes the provision of a process for the preparation of luminescentscreens for color television tubes which comprises exposing tocorpuscular radiation a light-insensitive composition comprising alight-insensitive organic binder layer containing inorganic phosphorparticles uniformly dispersed therein, said exposure being sufficient toeffect insolubilization of said binder material in the radiationstruckareas and thereafter treating said binder composition with aqueous mediawhereby to remove noninsolubilized portions, and wherein said organicbinder material comprises a member selected from the group consisting of(l) polymers, (2) monomers, and (3) mixtures of l) and (2) ofwater-soluble ethylenically unsaturated vinyl compounds containing atleast one grouping of the formula As specific examples of bindermaterials falling within the ambit of the foregoing definition there maybe mentioned in particular and without necessary limitation polyvinylpyrrolidone, polyethylene, polypropylene, polystyrene, polyvinylacetate, polyvinyl methyl ether, poly(methoxyethyl) vinyl ether;eopolymers including vinyl methyl ether/maleic anhydride, ethylene/-maleic anhydride, isobutyl vinyl ether/maleic anhydride, styrene/maleicanhydride, vinyl pyrrolidone/- maleic anhydride, poly(methoxyethyl)vinyl ether/- maleic anhydride, polyvinyl pyrrolidone/allyl amine;monomers including acrylamide, N,N'-methylenebisacrylamide, acrylicacid, methyl methacrylate, divinyl benzene, vinyl stearate, and thelike.

It is critically important to the realization of the improvementsdescribed herein that the organic binder material be light-insensitive.

Within the context of the present invention, the term"light-insensitivity is to be accorded the following significance. As iswell known, the polymerization, crosslinking etc. of many ethylenicallyunsaturated organic materials may be effected by exposure to certaintypes of electromagnetic radiation and especially ultra-violetradiation. Since many of such organic materials exhibit appreciablesensitivity to such spectral radiation the use of catalysts or otherpromotors to augment the reaction is completely unnecessary. Thus, theinsolubilization of organic polymeric resist materials is often carriedout by the utilization of electromagnetic radiation emanating from theviolet-blue region of the spectrum as the activating influence. In fact,the hardening reaction may occur merely upon standing ofsuch materialsfor relatively short periods of time. Ethylenically unsaturatedcompounds of this type prove unsuitable for use in the preparation ofluminescent screens for color television tubes in view of theirsensitivity to the radiation emitted by the blue phosphor upon electronbeam excitation, i.e., the blue-violet radiation emitted during theexposure interval is capable of initiating polymerization, cross-linkingetc. If ethylenic compounds of this type are to be used it becomesnecessary to omit the blue phosphor until exposure is completed.

in contradistinction to ethylenic materials of the aforedescribed type,the binder compounds contemplated by the present'invention remainunaffected 'by the radiation emissions of eachof the red, green and bluephosphor particles which occur during exposure. Thus, the blue phosphormay be present in the binder composition during the exposure step,thereby avoiding the multi-step procedure which would otherwise benecessary.

Particularly beneficial results are obtained in accordance with thepresent invention with the use of, for example, polymers of maleicanhydride, e.g., homopolymers, eopolymers with an alkyl vinyl ether,etc.

Maleic anhydride polymers preferred for use comprise those containingfrom about 10 percent to about 65 percent on a mole basis of maleicanhydride units with the remainder comprising, for example, alkyl vinylether units, the alkyl moiety containing from one to about carbon atoms,e.g., methyl, isobutyl, dodeeyl, hexadecyl, oetadecyl, .etc.; ethylene;propylene; styrene; etc. Polymers of this general type are commerciallyavailable from the General Aniline and Film Corporation under thetrademark designation GAN- TREZ," GANTREZ AN l49," which comprises acopolymer of maleic anhydride and methyl vinyl ether having a specificviscosity of 2.0 measured at 25C as a one percent solution in methylethyl ketone.

Polymeric materials of this type can be readily deposited in the form ofa uniform continuous layer according to conventional technique wherebyto provide a coated layer having the required stability and resistanceto viscosity changes upon standing. In general, it is found that thecoating operation may be facilitated by the employment of the polymericmaterial in specific viscosities ranging from about .05 to about 5.0 asmeasured in one percent solutions in methyl ethyl ketone at 25C. Optimumcoating solution viscosities within the foregoing range can be readilydetermined in a particular circumstance by routine laboratoryinvestigation.

The light-insensitive binder materials of the present invention may beutilized in the following manner. The electron beam-sensitive polymer,monomer or mixture thereof is first dissolved in aqueous media. Thephosphor particles are thereupon dispersed in the aqueous medium. Atthis point, it is usually desirable to effect any necessary viscosityadjustment in the solution, such adjustments being consonant withexpeditious deposition of the medium in the form ofa continuous anduniform coating of the desired thickness. The thickness value selectedis not a particularly critical factor in the practiceof the presentinvention and thus may be selected from those values customarilyemployed in the art for such purposes. In general, thinner coatings arepreferred in order to achieve the requisite degree of insolubilization.However, the coating thickness selected should be conducive to theprovision of a structurally stable coating whereby to permit theselective removal of non-insolubilized areas following exposure withoutdeleteriously affecting the exposed areas, e.g., undercutting. Thus,should the coating be excessively thin, inadvertent removal of exposedareas may result with consequent impairment of phosphor patternreproduction. It will also be appreciated that the solution viscosityvalue selected will be influenced to a great extent by the coatingmethod employed, i.e., flowing, whirling, etc. After allowing the layerthus deposited to dry, the shadow mask is positioned in the panel face.The picture tube. face and that portion of the tube housing the electronguns are accurately positioned against each other employing a gasket ofsuitable material along the area of contact. The tube assembly isthereupon evacuated. The shadow mask is then swept by an electron beamemanating from the appropriate electron gun, i.e., that gun whosecorpuscular emissions correspond to the particular color emittingphosphor pattern being laid down. Exposure is effected for a period oftime sufficient to impart the requisite insolubilization to those areassubjected to the electron beam. Upon completion of the exposure, air isadmitted to the system and the shadow mask retrieved. Thereupon, theshadow mask containing the latent image dot pattern in the form ofinsolubilized areas is treated with aqueous media whereby to effectremoval of non-exposed areas, the latter corresponding tonon-insolubilized portions. The foregoing sequence of operations isthereafter repeated for each of the remaining two primary colors wherebyto form a complete tricolor phosphor dot pattern.

Thereafter, the usual steps of lacquering, aluminizing, shadow maskinsertion, tube section sealing whereby to form an integral unit, bakingand evacuating to burn away the binder, may thereafter be resorted tofor purposes of providing the final product.

As the foregoing explanation makes clear, the process of the presentinvention makes possible the attainment of a most precise positionrelation between the electron gun, the shadow mask and the phosphor dotfor each of the three colors. The phosphor dot reproduction obtained isof distinctly superior quality, i.e., extremely sharp, bright andtotally free of metal contamination. This, of course, results inenhanced brilliance of emission upon electronic excitation of thephosphor. Moreover, and in contradistinction to processing involving theuse of photosensitive binders, overexposure to the electron beam doesnot result in exaggerated growth in the dot dimension; this resultobtains since the scattered light emissions emanatingfrom the phosphorparticles dispersed throughout the binder material are innocuous asregards imparting hardening effects to the binder material.

The term water-soluble as used in the context of the present inventionis intended to encompass those ethylenically unsaturated materials whichexhibit a sufficient degree of water-solubility, dispersibility orsensitivity to permit their expeditious coating in an aqueous system.Thus, it is recognized that particular circumstances dictate thefeasibility of providing the ethylenically unsaturated compound in theform of an aqueous dispersion, suspension, emulsion, etc. in order tofacilitate the attainment of an optimum coating. This can be readilyachieved by the use of suitable suspending agents, emulsifying agentsand dispersants well known in the art for such purposes. Regardless ofthe nature of the system employed for effecting deposition of theethylenic material in the form of a uniform coating, it will beunderstood that it remains a critical imperative that such organicmaterial be devoid of light-sensitivity as explained hereinbefore.

The present invention has been described with respect to certainpreferred embodiments thereof and there will become obvious to personsskilled in the art variations, modifications and equivalents which areunderstood as coming within the scope of the present invention.

I claim:

I. In a'process for the preparation of luminescent screens for colortelevision tubes, the improvement which consists essentially of thesequential steps of exposing to corpuscular radiation a surface coatedwith a corpuscular radiation sensitive composition consistingessentially of a water soluble organic binder layer insolubilizable bycorpuscular radiation containing inorganic phosphor particles uniformlydispersed therein, said organic binder material being unaffected byradiation emissions produced by said inorganic phosphor particles duringsaid exposure, said exposure being sufficient to effect insolubilizationof said binder material in the radiation-struck areas and thereaftertreating said binder composition with water whereby to remove onlyunexposed non-insolubilized portions, and wherein said organic bindermaterial comprises a member selected from the group consisting ofpolyvinyl pyrrolidone, polyethylene, polypropylene, polystyrene,polyvinyl methyl ether, poly (methoxy ethyl) vinyl ether, vinyl methylether/maleic anhydride copolymer, ethylene/maleic anhydride copolymer,isobutyl vinyl ether/maleic anhydride copolymer, styrene/maleicanhydride copolymer, vinyl pyrrolidone/maleic anhydride copolymer, poly(methoxy ethyl) vinyl ether/maleic anhydride copolymer, polyvinylpyrrolidone/allyl amine copolymer, acrylamide, N, N-methylenebisacrylamide, acrylic acid, methyl methylacrylate, divinylbenzene, vinyl stearate, and mixtures thereof.

2. A process according to claim 1 wherein said organic binder materialcomprises a copolymer of maleic anhydride and an alkyl vinyl etherwherein said alkyl moiety contains from one to about 20 carbon atoms andhas a specific viscosity ranging from about .05 to about 5.0 measured at25C as a one percent solution in methyl ethyl ketone.

3. A process according to claim 2 wherein said alkyl vinyl ethercomprises methyl vinyl ether.

4. A process according to claim 2 wherein said maleic anhydride/methylvinyl ether copolymer contains from about 10 percent to about percent ona mole basis of maleic anhydride and has a specific viscosity of 2.0measured at 25 as a one percent solution in methyl ethyl ketones.

5. A process according to claim 1 wherein said water contains a surfaceactive agent.

2. A process according to claim 1 wherein said organic binder materialcomprises a copolymer of maleic anhydride and an alkyl vinyl etherwherein said alkyl moiety contains from one to about 20 carbon atoms andhas a specific viscosity ranging from about .05 to about 5.0 measured at25*C as a one percent solution in methyl ethyl ketone.
 3. A processaccording to claim 2 wherein said alkyl vinyl ether comprises methylvinyl ether.
 4. A process according to claim 2 wherein said maleicanhydride/methyl vinyl ether copolymer contains from about 10 percent toabout 65 percent on a mole basis of maleic anhydride and has a specificviscosity of 2.0 measured at 25* as a one percent solution in methylethyl ketones.
 5. A process according to claim 1 wherein said watercontains a surface active agent.